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RE: st: Help about Ranksum - porder option

From   Roger Newson <>
Subject   RE: st: Help about Ranksum - porder option
Date   Mon, 31 Oct 2005 18:05:33 +0000

It is possible to get confidence limits corresponding to the -ranksum- test. If Óscar wants a confidence interval for the -porder- parameter, then one possibility is to use the -somersd- package, downloadable from SSC. If this is installed, then you can type

somersd control series, tr(c)

and -somersd- will print out a confidence interval for the -porder- parameter. The -somersd- package can also produce confidence limits for Somers' D.

If Óscar wants a confidence interval for the median difference between controlled and uncontrolled values of -series-, then this can be done with the program -cendif- (part of the -somersd- package). To do this, type

cendif series, by(control)

The -somersd- package can calculate a wide range of other confidence intervals for rank statistics, and these are described in the .pdf manuals distributed with -somersd-.

I hope this helps.


At 17:38 31/10/2005, Nick Cox wrote (in reply to Óscar Becerra):

A t test springs to mind, provided that its assumptions
are reasonably satisfied.

Plotting a graph springs even more to mind.


Óscar Becerra-CERAC

> Thanks, and can anyone suggests to me a procedure to perform
> this test?

Richard Goldstein

> porder is taking all possible pairs (control=yes paired with
> each control=
> no) and asking in what percent of those pairs is No larger
> than YES; this
> does not appear to be the question you are asking; if I
> correctly understand
> your question, I think you want a parametric procedure rather than the
> rank-sum test

Roger Newson
Lecturer in Medical Statistics
Department of Public Health Sciences
Division of Asthma, Allergy and Lung Biology
King's College London

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